1. Field of the Invention
The present invention is directed to a shielding apparatus for an arrangement of a pluggable connection of at least one light waveguide to a module chassis.
2. Description of the Prior Art
Related shielding designs have been disclosed, for example, by WO 94/12900. In accord therewith, a housing in which metallic guide sleeves, that project through a clearance of a backplane printed circuit board, are accepted is attached to the inside of the backplane printed circuit board of a module chassis. A plug connector from a light waveguide coming from the outside can be plugged onto the guide sleeves. The plug connector includes a metallic union nut that can be screwed to the guide sleeve. The backplane printed circuit board includes a shielding ply at its outside onto which a metallic member is applied; a metallic shielding sleeve being screwed thereto. The union nut and the shielding sleeve are extended beyond the plug.
In this region, the shielding sleeve includes spring tongues that have been cut free and that lie against a smooth-surfaced contact section of the union nut. The diameter of the clearance is of such a size that the guide sleeve or, respectively, the plug connector do not laterally touch the backplane printed circuit board in order to avoid a distortion of the plug connector arrangement. The clearance is electromagnetically closed and adequately shielded by the chimney-like shielding arrangement.
The present invention is therefore directed to an alternative shielding arrangement for the above-described configuration wherein the manufacturing and assembly outlay for such shielding arrangement may be greatly reduced.
Pursuant to the present invention, a guide sleeve can be of such a length that it not only projects into the clearance, but also through it. The shielding apparatus bridges the distance between the guide sleeve and the shielding ply over a short path. It directly contacts both the shielding ply and the guide sleeve so that intermediate contacts are eliminated. The shielding apparatus can be formed simply and cost-beneficially and requires little space; thus, simple assembly is enabled. The plug connection is substantially easier to access compared to an arrangement having a shielding sleeve that can be screwed in. As a result, the distance between neighboring plug connectors can be reduced.
The lateral resilience of the contact opening relative to the guide sleeve prevents lateral forces from being exerted thereon. Such forces, for example, can bend the slotted guide sleeve and deteriorate the optical connection quality.
The clearance can, for example, be formed as a through-plated bore connected to the shielding ply. The sleeve-shaped shielding apparatus can, for example, be composed of highly conductive elastomeric plastic and can include an inner, all around rib. The shielding apparatus is introduced into the bore and contacts the guide sleeve with the resilient rib. The lateral resilience of the shielding apparatus also yields a dependable contacting along the circumference of the shielding sleeve.
In an embodiment, the shielding apparatus can be punched in a simple way from a contact sheet of, for example, brass, bronze, Gennan silver or chrome-nickel steel. The circumference of the guide sleeve can include sharp-edged ribs pointing in longitudinal direction; for example, in the form of a knurl that presses itself into the smoothly circular contact opening. This yields a number of reliable contact locations that electromagnetically close the remaining gaps. The shielding apparatus can be connected to the shielding ply by soldering, for example. The shielding apparatus can be kept so thin that it does not impede the installation of other component parts.
In another embodiment, when the guide sleeve is plugged through, the contact tongues of the shielding apparatus are obliquely deflected out of the material plane so as to conform with resilient stress against, for example, the cylindrical outside cladding of the guide sleeve. This yields a dependable contacting given great lateral resilience, which enables a corresponding compensation of tolerances between the shielding apparatus and the guide sleeve.
In a further embodiment, a single shielding apparatus is particularly formed so as to contact a number of guide sleeves.
In another embodiment, the shielding apparatus is contacted with the shielding ply in a simple, clamping manner. A particular advantage of such embodiment is that the shielding apparatus can be delivered pre-mounted at the housing, so that any and all added outlay in the assembly of the module chassis is eliminated.
In yet a further embodiment, the shielding apparatus is centered at the housing. The centering openings can be kept such that the shielding apparatus clamps to them and is, thus, reliably held for final assembly.
Additional features and advantages of the present invention are described in, and will be apparent from, the Detailed Description of the Preferred Embodiments and the Drawings.